Muhammad Bakhsh Sobhi, Manzoor Ahmed Manzoor.
An in vitro study of change in working Length following instrumentation of 1st Molar Teeth.
J Coll Physicians Surg Pak Jan ;12(2):71-3.

Objective: To determine the mean reduction in working length following instrumentation of first molar canals. Design: An in vitro study to judge whether reduction in working length after preparation of curved canals is significant or not. Place and Duration of Study: This study was conducted at Armed Forces Institute of Dentistry (AFID), Rawalpindi (Pakistan) from 1 st January to 31 st March, 2001. Subjects and Methods: Total sixty; thirty each mandibular and maxillary teeth were selected. Their working length was measured before and after instrumentation of root canal system. Results: The canals having greatest curvature showed the greatest reduction in working length. The largest change was observed in the mesiobuccal canals of mandibular as well as maxillary first molar. None of the observed changes were statistically significant, as the P-value was more than 0.05. Conclusion: The decrease in working length following instrumentation of first permanent molar canals was not significant. Significant reduction in working length may lead to improper obturation of the root canal system and ultimately results into postoperative complications and onward failure of endodontic therapy.

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